feat(5.12): modal editare + cont obligatoriu la import; design.md + PRD 5.13 revizuit (/autoplan)

5.12 (livrat): editare in modal a randurilor de preview, cont obligatoriu inainte de
import, formular editare extras (_form_editare, _editare_preview_modal), plus suita de
teste aferenta (preview edit/compact, mapare op, form editare, signup, admin panel).

Design + planificare:
- docs/design.md: sistem de design (tokeni, breakpoints, scara control, componente, a11y).
- docs/prd/prd-5.12-* si prd-5.13-* (5.13 cu raport /autoplan: CEO+Design+Eng, audit trail).

Curatare: sterse PNG-urile de test/mockup temporare din radacina.

Nota: implementarea CSS 5.13 (responsive compact + sistem butoane) NU e inca facuta —
planul revizuit cere refactorul testelor fragile din test_web_responsive.py INAINTE de CSS.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

app/web/templates/signup.html

@@ -50,8 +50,8 @@
       <input type="text" name="name" value="{{ name or '' }}" required style="width:100%;">
     </p>
     <p>
-      <label>CUI <span style="color:var(--muted);font-size:12px;">(optional)</span></label><br>
-      <input type="text" name="cui" value="{{ cui or '' }}" style="width:100%;">
+      <label>CUI <span style="color:var(--err)">*</span></label><br>
+      <input type="text" name="cui" value="{{ cui or '' }}" required style="width:100%;">
     </p>
     <p>
       <label>Email <span style="color:var(--err)">*</span></label><br>